Dicyclopentadiene-modified phenolic resins have a lower dielectric constant and lower hygroscopicity than other phenolic resins. Therefore, resins obtained by epoxidizing the dicyclopentadiene-modified phenolic resins are useful as raw materials of semiconductor sealing agents and printed circuit boards.
Such a dicyclopentadiene-modified phenolic resin is produced by heating a phenol and a dicyclopentadiene in the presence of an acid catalyst. As the acid catalyst for this reaction, Lewis acids such as boron trifluoride, boron trifluoride phenol complex, and boron trifluoride ether complex and protonic acids such as sulfuric acid and para-toluenesulfonic acid have been used. However, any of these catalysts dissolves uniformly in the resulting product and thus cannot be used in recycling, and it is necessary to neutralize the catalyst with an alkali compound such as hydrotalcite or sodium hydroxide after the completion of the reaction. Furthermore, it is necessary to separate and collect the neutralizer and the deactivated catalyst from the product by filtering the reaction solution. Accordingly, there may be problems in that the step is complicated, a neutralizer and a filter aid are necessary, equipment such as a filter is necessary, the production time becomes long due to the filtration, and waste is generated each time the reaction is performed, resulting in an increase in the cost.
Patent Literature 1 discloses, in Claim 1, “a method for producing a phenol polymer, the method including allowing a phenolic compound and dicyclopentadiene to react with each other using a perfluoroalkane sulfonic acid ion-exchange resin as a catalyst”. From the 5th line to the 7th line on the upper left section of page (3) discloses that “the reaction is usually performed by thermal polymerization in the absence of a solvent . . . . However, use of a solvent inactive to the reaction does not cause any problem”. In addition, Advantageous Effects of Invention of page (4) discloses that “the phenol polymer produced is a good-quality polymer that contains no ionic impurities due to a residue of a catalyst component . . . , and the catalyst can be used repeatedly”.
Patent Literature 2 discloses, in Claim 1, a method in which a strongly acidic polystyrene-based ion-exchange resin is used as a catalyst. This method is advantageous in that a neutralizer is unnecessary and the amount of waste is reduced because the catalyst can be repeatedly used without neutralizing the catalyst.
Patent Literature 3 discloses a method for producing dicyclopentadiene-modified phenol by using a fixed-bed flow reactor filled with a solid acid and discloses that a fluorine-based ion-exchange membrane is used as the solid acid. Fluorine-based ion-exchange membranes are advantageous in that degradation due to a chemical reaction is less likely to occur than polystyrene-based ion-exchange resins.
Patent Literature 4 describes a step of dissolving a dicyclopentadiene-modified phenolic resin in an organic solvent, and removing an unreacted monomer, a catalyst, and so forth from the organic solvent with an aqueous solution of an alkali hydroxide (Claim 1). It is also disclosed that hydrochloric acid, sulfuric acid, phosphoric acid, and the like may be used for neutralizing an organic layer (from the 1st line to the 2nd line on the upper left section of page (3)). Patent Literature 5 describes a method for producing a dicyclopentadiene-modified phenolic resin, the method including adding an alkaline compound and zeolite to the resulting reaction product solution to deactivate the acid catalyst (Claim 1).